The instantaneous phase information is independent of trace amplitudes and it relates to the propagation phase of the seismic wavefront. Since, most of the time, wavefronts are defined as lines of constant phase, the phase attribute is also a physical attribute and can be effectively used as a discriminator for geometrical shape classifications.
- Best indicator of Lateral continuity, thus often used to track events
- Relates to the phase component of the wave propagation
- Can be used to compute the phase velocity
- Has no amplitude information, hence all events are represented
- Shows discontinuity, but may not be the best representation. It is better for showing continuity
- Shows seismic sequence boundaries
- A detailed visualization of bedding configurations
- Used to calculate instantaneous frequency and acceleration
This attribute usually has a relatively flat distribution ranging from + 180 at one end to -180 at the other. Phase wraps around on itself so common colorbars have the same color at the ends and different colors at 45 or 90-degree points. To us in interpretation, sharp changes can be defined at 45 or 90-degree points to help differentiate the different parts of the wavelet.
The instantaneous phase is the arctangent of the complex function imaginary value divided by the real trace value:
Where g(x,t) is the imaginary portion of the complex trace and f(x,t) is the real portion. There are some attributes that are calculated with an “un-wrapped” frequency where instead of going between -180 and 180 as this attribute does, it continues on in a positive phase display.
- Chopra, S. and K. J. Marfurt, 2007, Seismic attributes for prospect identification and reservoir characterization: Society of Exploration Geophysicists, Geophysical Developments #11.
- Taner, M. T., 2001, Seismic attributes: Canadian Society of Exploration Geophysicists Recorder, 26, no 7.